• a detailed description of the bug or problem you are having
• output of pip list from the virtual environment you are using
• pytest and operating system versions
• minimal example if possible

pytest: 9.0.2
operating system: any

When calling self.subTest(msg) with a non-string msg, the message is not printed when run via pytest.
In contrast, it is printed when run with unittest.
It is also printed when using the subtests fixture in a pytest test.

Example:

import unittest

class T(unittest.TestCase):
    def test_int_msg(self):
        with self.subTest(42):
            assert False, "subtest failure"

if __name__ == '__main__':
    unittest.main()

Run with unittest - message is printed:

FAIL: test_int_msg (__main__.T.test_int_msg) [42]

Run with pytest - message is replaced with <subtest>:

SUBFAILED(<subtest>) tests/subtest/test_subtest.py::T::test_int_msg - AssertionError: subtest failure

In contrast:

def test_int_msg(subtests):
    with subtests.test(42):
        assert False, "subtest failure"

Run with pytest - message is printed:

SUBFAILED[42] tests/subtest/test_subtest3.py::test_int_msg - AssertionError: subtest failure